SUSAN corner detector. More...
Functions | |
AFAPI features | susan (const array &in, const unsigned radius=3, const float diff_thr=32.0f, const float geom_thr=10.0f, const float feature_ratio=0.05f, const unsigned edge=3) |
C++ Interface for SUSAN corner detector. More... | |
AFAPI af_err | af_susan (af_features *out, const af_array in, const unsigned radius, const float diff_thr, const float geom_thr, const float feature_ratio, const unsigned edge) |
C Interface for SUSAN corner detector. More... | |
SUSAN corner detector.
SUSAN is an acronym standing for Smallest Univalue Segment Assimilating Nucleus. This method places a circular disc over the pixel to be tested (a.k.a nucleus) to compute the corner measure of that corresponding pixel. The region covered by the circular disc is M, and a pixel in this region is represented by \(\vec{m} \in M\) where \(\vec{m}_0\) is the nucleus. Every pixel in the region is compared to the nucleus using the following comparison function:
\( c(\vec{m}) = e^{-{(({I(\vec{m}) - I(\vec{m}_0))} / t})^6}\)
where t is radius of the region, I is the brightness of the pixel.
Response of SUSAN operator is given by the following equation:
\( R(M) = \begin{cases} g - n(M) \quad \text{if } n(M) < g\\ 0 \quad \text{otherwise},\\ \end{cases}\)
where \( n(M) = \sum\nolimits_{\vec{m} \in M} c(\vec{m})\), g is named the geometric threshold and n is the number of pixels in the mask which are within t of the nucleus.
Importance of the parameters, t and g is explained below:
AFAPI af_err af_susan | ( | af_features * | out, |
const af_array | in, | ||
const unsigned | radius, | ||
const float | diff_thr, | ||
const float | geom_thr, | ||
const float | feature_ratio, | ||
const unsigned | edge | ||
) |
C Interface for SUSAN corner detector.
[out] | out | is af_features struct composed of arrays for x and y coordinates, score, orientation and size of selected features |
[in] | in | is input grayscale/intensity image |
[in] | radius | nucleus radius for each pixel neighborhood |
[in] | diff_thr | intensity difference threshold a.k.a t from equations in description |
[in] | geom_thr | geometric threshold |
[in] | feature_ratio | is maximum number of features that will be returned by the function |
[in] | edge | indicates how many pixels width area should be skipped for corner detection |
in
is a 3d array, a batch operation will be performed. AFAPI features susan | ( | const array & | in, |
const unsigned | radius = 3 , |
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const float | diff_thr = 32.0f , |
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const float | geom_thr = 10.0f , |
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const float | feature_ratio = 0.05f , |
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const unsigned | edge = 3 |
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) |
C++ Interface for SUSAN corner detector.
[in] | in | is input grayscale/intensity image |
[in] | radius | nucleus radius for each pixel neighborhood |
[in] | diff_thr | intensity difference threshold |
[in] | geom_thr | geometric threshold a.k.a t from equations in description |
[in] | feature_ratio | is maximum number of features that will be returned by the function |
[in] | edge | indicates how many pixels width area should be skipped for corner detection |
in
is a 3d array, a batch operation will be performed.